Google EP276 and click "I'm Feeling Lucky" .. I think Zach accidentally told the plot of this story as a joke. Definitely accidental btw, I totally get that this is a coincidence, but it's bizarre how close they are.

Actually, there's a credible example for humans... that of the toxoplasmosis parasite, carried by a number of mammals, but primarily cats. We know that when it infects rats, it makes them much less wary of cats, even of their smell... so they're much more likely to get eaten.

We also know it can infect humans, usually without obvious symptoms. Now, a lot of humans are themselves pretty wary of cats... but then, there are "cat people", who seek them out at every opportunity. Not to mention the "crazy cat people", who hoard cats....

Yeah, definite similarities to "On a Blade of Grass." At least here it's a joke instead of the plot, but I have the same problem with it: how on earth would there be selection pressures that led to a parasite that reproduces in the stomach of an alien that it's never even been close to encountering?

(incidentally, my favorite parasites-make-people-do-normal-things story is "The Giving Plague" by David Brin)